Generate bindings code using a small syntax

[ngzhian]

Hi! I had an idea of generating bindings automatically:

1. Crawl website to generate some sort of simplified AST or a data format like YAML
2. A script to read in AST/data format to generate code

I wrote some code to do something like 2. pretty easily, you declare the bindings like so.

let auth_module =
                CModule("identity",
                  [CObject("AccountInfo", [("id", "string")])],
                  [CMethod("getAuthToken",
                           [("details", CObject(
                                "getAuthTokenOptions", [
                                  ("interactive", "Js.boolean");
                                  ("account", "accountInfo");
                                  ("scopes", "string list")
                                ]));
                            ("callback", CFn("string", "'a"
                              ))  
                           ])], []) in

Which generates

module Identity = struct
  class type _accountInfo = object
    method id : string
  end [@bs]
  type accountInfo = _accountInfo Js.t
  external mkAccountInfo : ?id:string -> unit -> accountInfo = "" [@@bs.obj]

  class type _getAuthTokenDetails = object
    method interactive : Js.boolean
    method account : accountInfo
    method scopes : string list
  end [@bs]
  type getAuthTokenDetails = _getAuthTokenDetails Js.t
  external mkGetAuthTokenDetails : ?interactive:Js.boolean -> ?account:accountInfo -> ?scopes:string list -> unit -> getAuthTokenDetails = "" [@@bs.obj]

  external getAuthToken : getAuthTokenDetails -> (string -> 'a) -> unit = "getAuthToken" [@@bs.scope "chrome", "identity"] [@@bs.val]

end

So you save some time writing all that boiler place.

Essentially the AST is simple, there are 3 types of chrome level exports, module, type, method; and there are 4 constructors to represent types (object, boolean, string, function/callback).

Right now the codegen is appending strings together (because this is hacked together, and also when I did some research on ocaml code generation projects one example i found used string concatenation). I was thinking it would be nice if we could directly generate OCaml AST, but this was easier to get up and running :)

I uploaded the code generation script on my fork of master, so if you'ld like, you can invoke it like so: ocamlc script.ml && ./a.out. I have an simple example module defined in the script itself just as a test.

Posting this here to see if there is any interest, I think with the script we can generate more 80% of the bindings to Chrome quite easily.